U.S. patent number 8,037,680 [Application Number 12/190,725] was granted by the patent office on 2011-10-18 for hydraulic control system for a swiveling construction machine.
This patent grant is currently assigned to Clark Equipment Company. Invention is credited to James M. Breuer, Alvin A. Liebel, Michael D. Wetzel.
United States Patent |
8,037,680 |
Breuer , et al. |
October 18, 2011 |
Hydraulic control system for a swiveling construction machine
Abstract
A hydraulic control system for a swiveling construction machine
includes at least one hydraulic travel motor, a first hydraulic
actuation device, a second hydraulic actuation device and a
hydraulic diverter valve assembly. The at least one hydraulic
travel motor is configured to move the swiveling construction
machine in a first travel speed and a second travel speed based on
a variable pilot pressure signal. The first hydraulic actuation
device is configured to actuate a first function of an implement.
The second hydraulic actuation device is configured to actuate a
second function of an implement. The hydraulic diverter valve
assembly is configured to divert hydraulic power between the first
hydraulic actuation device and the second hydraulic actuation
device while maintaining operation of the at least one hydraulic
travel motor in one of the first and the second speeds.
Inventors: |
Breuer; James M. (Mandan,
ND), Wetzel; Michael D. (Bismarck, ND), Liebel; Alvin
A. (Mandan, ND) |
Assignee: |
Clark Equipment Company (West
Fargo, ND)
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Family
ID: |
39865329 |
Appl.
No.: |
12/190,725 |
Filed: |
August 13, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090044434 A1 |
Feb 19, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60955512 |
Aug 13, 2007 |
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Current U.S.
Class: |
60/424;
37/410 |
Current CPC
Class: |
E02F
3/7613 (20130101); E02F 9/2285 (20130101); E02F
9/128 (20130101); E02F 9/2271 (20130101); E02F
3/964 (20130101); E02F 3/7618 (20130101); E02F
9/2267 (20130101) |
Current International
Class: |
E02F
9/22 (20060101); F15B 11/02 (20060101) |
Field of
Search: |
;60/420,424,426
;37/410 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10127898 |
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Mar 2002 |
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DE |
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1584824 |
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Oct 2005 |
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EP |
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2081777 |
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Feb 1982 |
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GB |
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11-269939 |
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Oct 1999 |
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JP |
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2002-81409 |
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Mar 2002 |
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JP |
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2002081409 |
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Mar 2002 |
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JP |
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2008/044094 |
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Apr 2008 |
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WO |
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Other References
Search Report and Written Opinion dated Nov. 17, 2008 for
International application No. PCT/US2008/009648. cited by
other.
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Primary Examiner: Lazo; Thomas E
Attorney, Agent or Firm: Farrell; Leanne Taveggia Westman,
Champlin & Kelly, P.A.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
The present application is based on and claims the benefit of U.S.
provisional patent application Ser. No. 60/955,512, filed Aug. 13,
2007, the content of which is hereby incorporated by reference in
its entirety.
Claims
What is claimed is:
1. A hydraulic control system for a swiveling construction machine
comprising: at least one hydraulic travel motor configured to move
a swiveling construction machine in a first speed and a second
speed based on a variable pilot pressure signal; a first hydraulic
actuation device configured to actuate a first function of an
implement; a second hydraulic actuation device configured to
actuate a second function of an implement; and a hydraulic diverter
valve assembly configured to divert hydraulic power between the
first hydraulic actuation device and the second hydraulic actuation
device while simultaneously maintaining operation of the at least
one hydraulic travel motor so that the at least one hydraulic
travel motor is capable of shifting between the first speed and the
second speed, the hydraulic diverter valve assembly coupled to the
variable pilot pressure signal and configured to divert the
hydraulic power between the first hydraulic actuation device and
the second hydraulic actuation device and shift the at least one
hydraulic travel motor based on a level of the variable pilot
pressure signal.
2. The hydraulic control system of claim 1, wherein the hydraulic
diverter valve assembly comprises a pair of actuator pressure
activated valves that are responsive to a first mid level pilot
pressure (P.sub.mid1) of the variable pilot pressure signal that is
between a first level of pressure (P.sub.0) and a second level of
pressure (P.sub.1), the actuator pressure activated valves
configured to divert hydraulic power from the second hydraulic
actuation device to the first hydraulic actuation device upon
receiving a pilot pressure greater than the first mid level pilot
pressure (P.sub.mid1).
3. The hydraulic control system of claim 2, wherein the hydraulic
diverter assembly comprises a travel motor pressure activated valve
responsive to a second mid level pilot pressure (P.sub.mid2) of the
variable pilot pressure signal that is between the second level of
pressure (P.sub.1) and a third level of pressure (P.sub.2), the
travel motor pressure activated valve configured to change the at
least one hydraulic travel motor from operating in the first speed
to operating in the second speed upon receiving a pilot pressure
greater than the second mid level pilot pressure (P.sub.mid2).
4. The hydraulic control system of claim 3, wherein the at least
one hydraulic travel motor is operated in the first speed when a
pilot pressure is at the first level of pressure (P.sub.0) or the
second level of pressure (P.sub.1) and wherein the at least one
hydraulic travel motor is operated in the second speed when a pilot
pressure is at the third level of pressure (P.sub.2).
5. The hydraulic control system of claim 2, wherein the hydraulic
diverter assembly further comprises a pair of relief valves coupled
to hydraulic lines that extend between the actuator pressure
activated valves and the second actuation device, the pair of
relief valves are configured to relieve pressure in the hydraulic
lines in response to pressures that exceed a threshold
pressure.
6. The hydraulic control system of claim 1, wherein the pilot
pressure signal is generated by a variable solenoid valve in a
pilot manifold, the variable solenoid valve is controlled by a
signal originating from a controller coupled to a joystick button
that is operable by an operator.
7. The hydraulic control system of claim 1, wherein the first
actuation device operates to raise and lower the work implement by
actuating a lift arm assembly that is coupled to the work
implement.
8. The hydraulic control system of claim 7, wherein the second
actuation device operates to angle the work implement by actuating
the work implement into an angle relative to the lift arm
assembly.
9. A swiveling construction vehicle comprising: an upperstructure
including a primary implement assembly, the upperstructure
configured to generate a variable pilot pressure signal; an
undercarriage comprising: a pair of rotatable track assemblies,
each track assembly rotated by a hydraulic travel motor that can be
operated in a first speed and a second speed; a secondary implement
assembly having a multi-function work implement controlled by the
variable pilot pressure signal, a first function of the work
implement is operable using a first hydraulic actuation device and
a second function of the work implement is operable using a second
hydraulic actuation device; a swivel coupling the upperstructure to
the undercarriage, the swivel configured to allow the
upperstructure to rotate relative to the undercarriage and to
accommodate hydraulic lines and a line for the variable pilot
pressure signal that extends between the upperstructure and the
undercarriage; and a hydraulic diverter valve assembly housed in
the undercarriage and configured to divert hydraulic power between
the first hydraulic actuation device and the second hydraulic
actuation device while simultaneously maintaining operation of each
hydraulic travel motor so that each hydraulic travel motor is
capable of shifting between the first and the second speeds, the
hydraulic diverter valve assembly coupled to the pilot pressure
signal and configured to divert the hydraulic power and shift each
hydraulic travel motor based on a level of the variable pilot
pressure signal.
10. The swiveling construction vehicle of claim 9, wherein the
diverter valve assembly comprises a pair of actuator pressure
activated valves that are responsive to a first mid level pilot
pressure (P.sub.mid1) of the variable pilot pressure signal that is
between a first level of pressure (P.sub.0) and a second level of
pressure (P.sub.1), the actuator pressure activated valves
configured to divert hydraulic power from the second hydraulic
actuation device to the first hydraulic actuation device upon
receiving a pilot pressure greater than the first mid level pilot
pressure (P.sub.mid1).
11. The swiveling construction vehicle of claim 10, wherein the
diverter assembly comprises a travel motor pressure activated valve
responsive to a second mid level pilot pressure (P.sub.mid2) of the
variable pilot pressure signal that is between the second level of
pressure (P.sub.1) and a third level of pressure (P.sub.2), the
travel motor pressure activated valve configured to change the at
least one hydraulic travel motor from operating in the first speed
to operating in the second speed upon receiving a pilot pressure
that is greater than the second mid level pilot pressure
(P.sub.mid2).
12. The hydraulic control system of claim 11, wherein the hydraulic
travel motors are operated in the first speed when a pilot pressure
is at the first level of pressure (P.sub.0) or at the second level
of pressure (P.sub.1) of the variable pilot pressure signal and
wherein the hydraulic travel motors are operated in the second
speed when a pilot pressure is at the third level (P.sub.2) of
pressure.
13. The swiveling construction vehicle of claim 10, wherein the
hydraulic diverter assembly further comprises a pair of relief
valves coupled to hydraulic lines that extend between the actuator
pressure activated valves and the second actuation device, the pair
of relief valves are configured to relieve pressure in the
hydraulic lines in response to pressures that exceed a threshold
pressure.
14. The swiveling construction vehicle of claim 9, wherein the
pilot pressure signal is generated by a variable solenoid valve in
a pilot manifold, the variable solenoid valve is controlled by a
signal originating from a controller coupled to a joystick button
that is operable by an operator in an operator support portion of
the upperstructure.
15. The swiveling construction vehicle of claim 9, wherein the
first actuation device operates to raise and lower the work
implement by actuating a lift arm assembly that is coupled to the
multi-function work implement.
16. The swiveling construction vehicle of claim 15, wherein the
second actuation device operates to angle the multi-function work
implement by actuating the multi-function work implement into an
angle relative to the lift arm assembly.
17. A method of modifying an excavator that operates a
single-function work implement on a undercarriage to operating a
multi-function work implement on the undercarriage, the method
comprising: providing an excavator comprising: an upperstructure;
an undercarriage; a hydraulic swivel that rotatably couples the
upperstructure to the undercarriage and houses hydraulic
connections that extend between the upperstructure and the
undercarriage; a pair of hydraulic travel motors; a multi-function
work implement coupled to the undercarriage; a first hydraulic
actuation device configured to operate a first function of the
multi-function work implement; a second hydraulic actuation device
configured to operate a second function of the multi-function work
implement; installing a hydraulic diverter valve assembly in the
undercarriage, the diverter valve assembly configured to divert
hydraulic power between the first hydraulic actuation device and
the second hydraulic actuation device while maintaining operation
of each hydraulic travel motor in one of a first and a second
speed, the hydraulic diverter valve assembly coupled to a variable
pilot pressure signal from the upperstructure and configured to
divert the hydraulic power based on a level of the variable pilot
pressure signal; and changing controls in the upperstructure to
coordinate with the diverter valve assembly.
18. The method of claim 17, wherein the hydraulic diverter valve
assembly comprises a pair of actuator pressure activated valves
that are responsive to a first mid level pilot pressure
(P.sub.mid1) of the variable pilot pressure signal that is between
a first level of pressure (P.sub.0) and a second level of pressure
(P.sub.1), the actuator pressure activated valves configured to
divert hydraulic pressure from the second hydraulic actuation
device to the first hydraulic actuation device upon receiving a
pilot pressure greater than the first mid level pilot pressure
(P.sub.mid1).
19. The method of claim 18, wherein the hydraulic diverter assembly
comprises a travel motor pressure activated valve responsive to a
second mid level pilot pressure (P.sub.mid2) of the variable pilot
pressure signal that is between the second level of pressure
(P.sub.1) and a third level of pressure (P.sub.2), the travel motor
pressure activated valve is configured to change the at least one
hydraulic travel motor from operating in the first speed to
operating in the second speed upon receiving a pilot pressure that
is greater than the second mid level pilot pressure
(P.sub.mid2).
20. The method of claim 19, wherein changing the controls in the
upperstructure to coordinate with the hydraulic diverter valve
assembly comprises: changing the controls in the upperstructure
such that first, second and third modes of pilot pressure can be
sent to the diverter assembly; wherein, in the first mode, a second
level of pilot pressure (P.sub.1) is set and therefore the actuator
pressure activated valves are activated to route hydraulic power to
the first actuation device and maintain the hydraulic motors in the
first speed; wherein, when switching between the first mode and the
second mode, a third level of pilot pressure (P.sub.2) is set and
therefore the travel motor pressure activated valve is activated to
route hydraulic power to the travel motors to change the travel
motors from the first speed to the second speed while the actuator
pressure activated valves remain activated and maintain hydraulic
power routed to the first actuation device; and wherein, when
switching between the first mode and the third mode, a first level
of pilot pressure (P.sub.0) is set and therefore the actuator
pressure activated valves are deactivated and route hydraulic power
to the second actuation device and maintain the hydraulic motors in
the first speed.
Description
BACKGROUND OF THE INVENTION
An excavator is a tracked swiveling construction vehicle that
includes an undercarriage that supports a pair of track assemblies
and an upperstructure that includes an operator support portion.
The pair of track assemblies are powered by motors and are
controlled by an operator located in the cab. The undercarriage is
equipped with a dozer blade that is fixed to a lift arm also
controlled by the operator. Pinned to the upperstructure is an
implement assembly including a boom and arm.
The implement assembly includes a bucket, breaker or other
attachment coupled to the arm that is configured for excavating and
trenching. In operation, the dozer blade is used for grading,
leveling, backfilling, trenching and general dozing work. The blade
can be used to increase dump height and digging depth depending on
its position in relation to the boom and implement assembly. The
blade also serves as a stabilizer during digging operations.
The upperstructure can rotate relative to the undercarriage by a
swivel. Any hydraulic power that is transmitted to the
undercarriage from the upperstructure is typically routed through
the hydraulic swivel. For example, travel motors, such as the
motors that power the pair of track assemblies, and tools, such as
the dozer blade located on the undercarriage, can require hydraulic
power. Routing hydraulic fluid through the swivel is complicated by
the 360 degree rotation of the upperstructure relative to the
undercarriage.
Since the hydraulic connections routed through the swivel are
hard-plumbed into the swivel, adding new hydraulically-controlled
features to the undercarriage generally requires the design and
installation of a unique swivel for each version of an excavator.
In addition, each new hydraulic line for each new
hydraulically-controlled feature typically requires a separate
control mechanism in the upperstructure. Creating and installing a
unique swivel and adding separate control mechanisms for each
version of an excavator can incur added costs and complexity to the
manufacturing process of excavators.
The discussion above is merely provided for general background
information and is not intended to be used as an aid in determining
the scope of the claimed subject matter.
SUMMARY OF THE INVENTION
A hydraulic control system for a swiveling construction machine
includes at least one hydraulic travel motor, a first hydraulic
actuation device, a second hydraulic actuation device and a
hydraulic diverter valve assembly. The at least one hydraulic motor
is configured to move the swiveling construction machine in a first
speed and a second speed based on a variable pilot pressure signal.
The first hydraulic actuation device is configured to actuate a
first function of an implement. The second hydraulic actuation
device is configured to actuate a second function of an implement.
The hydraulic diverter valve assembly is configured to divert
hydraulic power between the first hydraulic actuation device and
the second hydraulic actuation device while maintaining operation
of the at least one hydraulic travel motor in one of the first and
the second speeds. The at least one hydraulic travel motor, the
first hydraulic actuation device, the second hydraulic actuation
device and the hydraulic diverter valve assembly can all be coupled
to an undercarriage in the swiveling construction vehicle and the
variable pilot pressure signal can be generated from the pilot
manifold of the swiveling construction vehicle.
These and various other features and advantages will be apparent
from a reading of the following Detailed Description. This Summary
is not intended to identify key features or essential features of
the claimed subject matter, nor is it intended to be used as an aid
in determining the scope of the claimed subject matter. The claimed
subject matter is not limited to implementations that solve any or
all disadvantages noted in the background.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a perspective view of a prior art excavator.
FIG. 2 illustrates a schematic block diagram of a hydraulic control
system in the excavator illustrated in FIG. 1.
FIG. 3 illustrates a perspective view of an excavator under one
embodiment.
FIG. 4 illustrates a schematic block diagram of a hydraulic control
system implemented in the excavator illustrated in FIG. 3.
FIG. 5 illustrates a schematic block diagram of a hydraulic control
system implemented in the excavator illustrated in FIG. 3.
FIG. 6 illustrates a side view of the excavator illustrated in FIG.
3.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Embodiments of the disclosure describe a way to modify an existing
swiveling construction machine to add an additional hydraulic
control to the undercarriage without having to change the swivel
itself, and with minimal changes to the controls in the
upperstructure of the machine. In particular, embodiments of the
disclosure describe ways that multi-function tools or implements
can be added to the undercarriage of the machine after manufacture
without having to change the swivel and only having to make minimal
changes to the controls. For example, an excavator (a type of
swiveling construction machine) could be manufactured with a
single-function tool coupled to the undercarriage. For example, a
normal dozer blade includes the single-function of lifting.
However, the single-function tool could be replaced with a
multi-function tool. For example, an angled dozer blade includes
the function of lifting as well as the function of angling.
FIG. 1 illustrates a perspective view of a prior art compact
excavator 100. Compact excavator 100 includes an undercarriage 104,
an upperstructure 106 including an operator support structure 108
and a primary implement assembly 110 pinned to upperstructure 106.
Primary implement assembly 110 includes a boom 112, an arm 114 and
an arm mounted attachment 116. As illustrated in FIG. 1, arm
mounted attachment 116 is a bucket. However, those skilled in the
art will recognize that other types of attachments can be used,
such as a breaker or an auger.
Undercarriage 104 is configured to support a pair of tracking
assemblies 118 located on the left and right sides of compact
excavator 100. Each track assembly 118 includes a track 120 that is
rotatable about a sprocket 122 (only one sprocket is shown in FIG.
1). Each sprocket 122 is powered by a travel motor controlled
through manipulation of suitable controls in operator support
structure 108.
FIG. 2 illustrates a schematic diagram of a hydraulic control
system 130 for an excavator, such as excavator 100. Some swiveling
construction machines or excavators, such as excavator 100 (FIG.
1), utilize a pilot signal 133 to change the speed of hydraulic
travel motors 132 that power each sprocket 122 (FIG. 1) of the each
track assembly 118 (FIG. 1). For example, each hydraulic travel
motor 132 for each track assembly 118 can be a two-speed travel
motor that is toggled between a first or low speed and a second or
high speed. The pilot signal 133 is generated by a pilot manifold
134 in the upperstructure 106. In such an arrangement, the pilot
signal 133 varies between a low pressure (possibly even zero
pressure) and a high pressure. For example, the motors 132 can be
toggled between the two speeds by momentarily pressing a button on
a joystick. A computer or other electronic controller in the
machine receives the signal from the button and changes the state
of the pilot manifold or solenoid valve, such that the output pilot
pressure is high or low as appropriate. The high or low pilot
pressure signal 133 is then transmitted to the travel motors 132 to
switch between the first and second speed modes.
Referring back to FIG. 1, compact excavator 100 also includes a
secondary implement assembly 124. Secondary implement assembly 124
is attached to undercarriage 104 of compact excavator 100.
Secondary implement assembly 124 includes a lift arm assembly 126
and a work tool or implement 128. Lift arm assembly 126 is
pivotally coupled to undercarriage 104. Lift arm assembly 126 is
configured to rotate through an arc centered on a lift arm pivot
axis upon actuation by a pair of hydraulic actuators 127. Work tool
128 is a single-function tool. In particular and as illustrated in
FIG. 1, work tool 128 is a dozer blade. However, it should be
realized that work tool 128 can be other types of implements. In
operation, the dozer blade 128 is used for grading, leveling,
backfilling, trenching and general dozing work. The blade can be
used to increase dump height and digging depth depending on its
position in relation to the boom and implement assembly. The blade
also serves as a stabilizer during digging operations. In general,
the single-function dozer blade is limited to the range of motion
of lift arm assembly 126.
Referring to FIG. 2, hydraulic control system 130 illustrates the
hydraulics used to operate hydraulic actuators 127 coupled to lift
arm assembly 126 (FIG. 1). It should be realized that some
swiveling construction machines or excavators, include a separate
system from the hydraulic travel system for operating the hydraulic
actuators 127 coupled to the lift arm assembly 126. However, in
FIG. 2, both systems are shown as hydraulic control system 130. The
hydraulic actuators 127 operate to control the lift or height of
the work tool 128 using a main control valve 135 in the operator
support structure 108 of the upperstructure 106. For example, the
lifting or lowering of lift arm assembly 126 is controlled by a
joystick or lever, where moving the joystick or lever raises and
lowers the blade. In addition, hydraulic control system 130 can
also include a return or overflow hydraulic tank 136 located in the
upperstructure 106 of compact excavator 100.
Each of the hydraulic components that are housed in the
upperstructure of an excavator, such as upperstructure 106 of
excavator 100, are coupled to an undercarriage, such as
undercarriage 104, through a fluid-tight hydraulic swivel 138. A
plurality of fluid-tight swivel connectors are included in
hydraulic swivel 138 and are designed to couple a set of hydraulic
lines. The fluid-tight swivel connections allow the upperstructure
106 to rotate relative to the undercarriage 104 via a slew bearing
in a full 360 degrees. While the use of flexible hoses or tubing
can also provide a fluid-tight coupling instead of the use of a
hydraulic swivel, the flexible hoses or tubing provide limited
rotation by not allowing continuous 360 degrees of movement. To
allow a 360 degree rotation, a fluid-tight hydraulic swivel is used
in swiveling construction machines to provide multiple hydraulic
fluid connections across a continuously rotatable interface.
When the need arises for an additional, separately controllable
hydraulic line in the undercarriage that was not previously put in
place at the time of manufacture of the excavator, usually a
different hydraulic swivel is installed. For example, if a
single-function tool in an existing excavator is swapped out for a
multi-function tool, a different hydraulic swivel is also installed
in the existing excavator to accommodate the need for the separate
controllable hydraulic lines. Although a more complex hydraulic
swivel could be installed at manufacture to accommodate any new
hydraulic fluid lines for the future, this would require multiple
different versions of the machine to be manufactured depending the
types of tools that will be added to the undercarriage. Installing
a different hydraulic swivel is laborious and difficult and making
multiple versions of a machine increases complexity and cost in the
manufacturing process. Therefore, embodiments discussed below
modify an excavator to hydraulically control a multi-function tool
instead of a single-function tool without installing a different
hydraulic swivel.
FIG. 3 illustrates a perspective view of a compact excavator 200
under one embodiment. Like compact excavator 100 of FIG. 1,
excavator 200 includes an undercarriage 204, an upperstructure 206
including an operator support structure 208 and a primary implement
assembly 210 pinned to upperstructure 206. Primary implement
assembly 210 includes a boom 212, an arm 214 and an arm mounted
attachment 216.
Undercarriage 204 supports a pair of tracking assemblies 218
located on the left and right sides of compact excavator 200. Each
track assembly 218 includes a track 220 that is rotatable about a
sprocket 222 (only one sprocket is shown in FIG. 3). Each sprocket
222 is powered by a hydraulic travel motor controlled through
manipulation of suitable controls in operator support structure
208.
Compact excavator 200 also includes a secondary implement assembly
224. Secondary implement assembly 224 is attached to undercarriage
204 of compact excavator 200. Secondary implement assembly 224
includes a work tool or implement 228. In the FIG. 3 embodiment,
work tool 228 is a multi-function tool instead of the
single-function tool 128 illustrated in FIG. 1. Like work tool 128,
work tool 228 can perform the functions of the single-function work
tool using a first actuation device 227 (i.e., a pair of lift arm
hydraulic actuators). In the embodiment illustrated in FIG. 3, a
lift arm assembly 226 is pivotally coupled to undercarriage 204.
Lift arm assembly 226 is configured to rotate through an arc
centered on a lift arm pivot axis upon actuation by the first
actuation device or pair of lift arm hydraulic actuators 227.
However, in addition to this first function, work tool 228 can
perform further functions. For example, secondary implement
assembly 224 further includes a second actuation device 229. In
FIG. 3, second actuation device 229 is an angle hydraulic actuator.
In the embodiment where work tool 228 is an angled dozer blade 228,
angle hydraulic actuator 229 can angle blade 228 to the side, which
provides work tool 228 with more functionality than that of dozer
blade 128. This sidewise motion is illustrated in FIG. 3.
It should be realized that other types of multi-function work tools
with at least a first actuation device and a second actuation
device can be coupled to undercarriage 204 for use in excavating
than that of the angled dozer blade that is illustrated in FIG. 3.
For example, an angled sweeping tool can be added to undercarriage
204. A first actuation device attached to the undercarriage 204 can
utilize hydraulic power to adjust a sweeping angle of the sweeping
tool to the side. A second actuation device attached to the
undercarriage 204 can utilize hydraulic power to rotate the
sweeper. In another example, a forklift attachment can be added to
undercarriage 204. A first actuation device attached to
undercarriage 204 can utilize hydraulic power to adjust the height
of the fork. A second actuation device attached to undercarriage
204 can utilize hydraulic power to adjust the angle of the fork
relative to horizontal.
FIG. 4 illustrates a schematic diagram of a hydraulic control
system 230 for a swiveling construction machine or excavator 200
(FIG. 3) under one embodiment. To allow a multi-function tool to be
coupled to the secondary implement assembly 224 (FIG. 3) without
having to install a different hydraulic swivel, as discussed above,
a hydraulic diverter valve assembly 240 is installed in a hydraulic
control system 230 of excavator 200. More specifically, hydraulic
diverter valve assembly 240 is installed on the undercarriage 204
of excavator 200 and is controlled by a variable pressure pilot
signal 233. The hydraulic diverter valve assembly 240 can be used
to divert hydraulic power between a first actuation device 227,
such as lift actuators 227 on secondary implement assembly 224
(FIG. 3), and a second actuation device 229, such as angle actuator
229 that is also attached to secondary implement assembly 224.
Hydraulic diverter valve assembly 240 includes a collection of
pressure activated valves 246, 252 and 258 that are operably
connected to the pilot pressure signal line 233 as well as valves
246 and 252 to the hydraulic power supply lines 242 and 243 for
powering the first actuation device 227 and the second actuation
device 229 of work tool 228 (FIG. 3). Each pressure activated valve
246, 252 and 258 has an input 247, 253, 259 for the line of the
variable pilot pressure signal line 233. Each of the pressure
activated valves 246 and 252 have an input 248 and 254 for one of
the hydraulic power supply lines 242 and 243 that extend from a
main control valve 235 in the upperstructure 206 of excavator 200
(FIG. 3). Each of the pressure activated valves 246 and 252 have
two outputs 249, 250 and 255, 256 for routing hydraulic power to
first actuation device 227 and second actuation device 229,
respectively.
FIG. 5 illustrates a more basic schematic block diagram of the
hydraulic control system 230 illustrated in FIG. 4. Using the
variable pilot pressure signal 233, diverter valve assembly 240
operates to switch the hydraulic power between the first actuation
device 227 and the second actuation device 229. To accomplish this,
pilot pressure signal 233 is generated by a pilot manifold or
variable solenoid valve 234. In one embodiment, the variable
solenoid valve 234 is controlled by a pulse-width modulated (PWM)
signal 264 originating from a controller 266 via a joystick button
262 that is actuated by an operator located in upperstructure
206.
In one embodiment, variable pilot pressure signal 233 is varied
between a first level of pressure or low pressure (P.sub.0), a
second level of pressure or intermediate pressure (P.sub.1) and
third level of pressure or high pressure (P.sub.2). Variable pilot
pressure signal 233 is transmitted from upperstructure 206 to
undercarriage 204 through hydraulic swivel 238, and is then
connected to hydraulic diverter valve assembly 240. With reference
back to FIG. 4, in hydraulic diverter valve assembly 240, variable
pilot pressure signal 233 is routed to a travel motor pressure
activated valve 258 and one or more actuator pressure activated
valves 246 and 252. In one embodiment, the pressure activated
valves 246, 252 and 258 can be valves having pressure controlled
springs, where the stiffness of the spring determines the pressure
at which the valve switches from one state to another.
In one embodiment, the pair of actuator pressure activated valves
246 and 252 are responsive to a first mid level pressure P.sub.mid1
(i.e., a pressure between first level of pressure P.sub.0 and
second level of pressure P.sub.1) and are used to connect the
hydraulic power from main control valve 235 to either first
actuation device 227 or to second actuation device 229 of the work
tool 228 (FIG. 3) based on a level of the variable pilot pressure
signal. When the pilot pressure signal is at a level of pressure
that is less than first mid level pressure P.sub.mid1, such as
first level of pressure P.sub.0, the hydraulic power from the main
control valve 235 is routed by the actuator pressure activated
valves 246 and 252 to the second actuation device 229. When the
pilot pressure signal is at a level of pressure that is greater
than first mid level pressure P.sub.mid1, such as second level of
pressure P.sub.1 or third level of pressure third level of pressure
P.sub.2 the hydraulic power from main control valve 235 is routed
by the actuator pressure activated valves 246 and 252 to first
actuation device 227.
In another embodiment, an output 260 of travel motor pressure
activated valve 258 opens in response to a second mid level
pressure P.sub.mid2 (i.e., a pressure between second level of
pressure P.sub.1 and third level of pressure P.sub.2) and is then
routed out of hydraulic diverter valve assembly 240 to travel
motors 232. Therefore, a pilot pressure signal at a level below
second mid level pressure P.sub.mid2 puts travel motors 232 located
in undercarriage 204 in a first or low speed mode, while a pilot
pressure signal at a level above second mid level pressure
P.sub.mid2 puts travel motors 232 in a second or high speed
mode.
As previously discussed, in the embodiment illustrated in FIGS.
3-5, first actuation device 227 includes a pair of lift actuators
227 for raising and lowering work tool 228, while second actuation
device 229 includes an angle actuator 229 for angling work tool
228. In the embodiment illustrated in FIG. 4, one of the pair of
actuator pressure activated valves 252 is connected to the base
side 270 and 271 of each actuator 227 and 229, while the other of
the pair of actuator pressure activated valves 246 is connected to
the rod side 272 and 273 of each actuator 227 and 229.
When considering the first level of pressure or low pressure
(P.sub.0), the second level of pressure or intermediate pressure
(P.sub.1) and the third level of pressure or high pressure
(P.sub.2) of the pilot signal and the thresholds for activation of
the pressure activated valves 246, 252 and 258, namely that first
mid level pressure P.sub.mid1 is between P.sub.0 and P.sub.1 and
second mid level pressure P.sub.mid2 is between P.sub.1 and
P.sub.2, the following table can be constructed:
TABLE-US-00001 Mode 3 1 2 Pilot Pressure P.sub.0 P.sub.1 P.sub.2
Actuator P.sub.mid1 activated valves 246 and 252 Travel motor
P.sub.mid2 activated valve 258 Low speed X X travel High speed X
travel First actuation X X device 227 Second X actuation device
229
In one embodiment, mode 3 is activated by holding down joystick
button 262 continuously for at least 0.5 seconds, for example. The
hydraulic control system 230 (FIGS. 4 and 5) of excavator 200 (FIG.
3) remains in mode 3 for as long as the joystick button 262 is held
down. While in mode 3, movement of the joystick 261 activates
second actuation device 229 (e.g., changes the angle of dozer blade
228 (FIG. 3)). When the excavator's hydraulic control system 230
detects a continuous button hold for more than 0.5 seconds, the
controller sends the appropriated signal, via PWM, to the pilot
manifold 234 (FIGS. 4 and 5) to deliver a pilot pressure of
P.sub.0. Given the responsiveness of the travel motor and actuator
pressure activated valves 246, 252 and 258 (FIG. 4) in diverter
valve assembly 240 (FIGS. 4 and 5), this pilot pressure level puts
the travel motors 232 (FIGS. 4 and 5) in low speed and transfers
hydraulic power to the second actuation device 229 (FIGS. 4 and 5).
Release of joystick button 262 reverts the pilot pressure signal
back to mode 1.
When the button is momentarily pressed (e.g., less than 0.5
seconds) and released, the system switches between modes 1 and 2.
In mode 1, the machine's controller 266 signals the pilot manifold
234, via PWM, to set the pilot pressure at second level of pressure
P.sub.1. At this intermediate pressure P.sub.1, the actuator
pressure activated valves 246 and 252 route the hydraulic power to
the first actuation device 227 (e.g., activates lift actuators to
raise or lower dozer blade 228) while the travel motors 232 are
signaled by the travel motor pressure activated valve 258 to be in
low speed.
When switching from mode 1 to mode 2, actuator pressure activated
valves 246 and 252 remain in the same state, since in both mode 1
and mode 2 the pressure is greater than first mid level pressure
P.sub.mid1. Therefore, in mode 2, first actuation device 227
continues to be powered. In both modes 1 and 2, movement of the
joystick causes the first actuation device 227 to cause dozer blade
228 or other type of implement to move up and down. In mode 2,
pressure is at third level of pressure P.sub.2, which is
sufficiently elevated (i.e., above second mid level pressure
P.sub.mid2) to change travel motors 232 from the first speed to the
second speed. In one embodiment, the pressure at which the
two-speed travel motors 232 switch from the first to the second
speed may be less than third level of pressure P.sub.2, but the
motor speed will not change until the pilot pressure signal 233 is
above the second mid level of pressure P.sub.mid2 because travel
motor pressure activated valve 258 does not divert the pilot
pressure signal 233 to the motors 232 until the second mid level of
pressure P.sub.mid2 is reached (e.g., until the pilot pressure 233
is set to third level of pressure P.sub.2).
In each case, the position of joystick button 262 is monitored by a
computer or other electronic controller 266, which translates the
button signal into a PWM signal that causes the pilot pressure
manifold 234 to generate the appropriate pilot pressure signal 233
(FIGS. 4 and 5).
In the embodiment illustrated in FIG. 4, diverter valve assembly
240 also includes one or more relief valves 276 and 278 in-line
with the hydraulic power lines to angle actuator 229, at either or
both of the base 271 and the rod sides 273. These relief valves 276
and 278 are configured to relieve pressure in the hydraulic lines
in response to pressures that exceed a threshold pressure. In one
example, the threshold pressure is set at 4000 psi. At 4000 psi,
relief valves 276 and 278 will open to relieve the hydraulic
pressure in the line caused by the dozer blade or other implement
228 hitting an obstruction that can generate pressure on the angle
actuator 229. Upon opening of a relief valve 276 or 278, some
excess hydraulic fluid is sent to the return or hydraulic tank 236
(FIG. 4).
The advantages of this system will be apparent to those skilled in
the art and will be discussed thoroughly with FIG. 6. FIG. 6
illustrates a side view of excavator 200 with some components
visible that would otherwise not be. As previously discussed,
control system 230 includes components on upperstructure 206 and on
undercarriage 204. Components on upperstructure 206 include a
joystick 261 with joystick button 262, a controller 266, a main
control valve 235 and a pilot valve or manifold 234. Coupling the
upperstructure 206 to undercarriage 204 is a swivel bearing 237.
The swivel bearing 237 allows upperstructure 206 to rotate relative
to undercarriage 204. Hydraulic power transmitted from
upperstructure 206 to undercarriage 204 is routed through hydraulic
swivel 238. Components on undercarriage 204 include a hydraulic
diverter valve assembly 240, lift actuators 227, angle actuator
229, travel motors 232 and a dozer blade or other type of implement
228.
The hydraulic control system 230 (also illustrated in FIGS. 4 and
5) in excavator 200 can be used to separately control additional
hydraulic components on the undercarriage 204. In upperstructure
206 of excavator 200, the electronic controls can be modified to
recognize a continuous push of the joystick button 262 and to
transmit the appropriate PWM signal 264 (FIG. 5) to pilot pressure
manifold 234 to change the pilot pressure accordingly. In the
undercarriage 204, hydraulic diverter valve assembly 240 can be
installed such that the pilot pressure signal 233 (FIGS. 4 and 5)
is transmitted through the hydraulic diverter valve assembly 240
and then coupled to travel motors 232 and lift and angle actuators
227 and 229.
As previously discussed, the approach of using a multiplexed pilot
signal to control several different hydraulic cylinders on
undercarriage 204, using an existing hydraulic swivel 238, can be
generalized to other tools besides an angled dozer blade that is
illustrated in FIGS. 3 and 6. In one embodiment, a six way dozer
blade can be added, so that in a first mode, the hydraulic power
from main control valve 235 controls an actuator that adjusts the
dozer blade angle and in a second mode, the hydraulic power adjusts
the dozer blade oscillation. In another embodiment, a forklift
attachment can be added to undercarriage 204, so that in a first
mode the hydraulic power from main control valve 235 controls an
actuator to adjust the height of the fork and in a second mode, the
hydraulic power from main control valve 235 controls an actuator to
adjust the angle of the fork relative to horizontal.
One skilled in the art will also recognize that the principles of
the above-discussed hydraulic system can be used to provide a
greater degree of multiplexing so that more than two separate
functions can be operated with a single pilot signal and hydraulic
power line. Adding a wider range of intermediate pressure control
valves permits three or more hydraulic devices to be controlled
independently, based on the pressure level of the variable pressure
pilot signal. To achieve these additional levels of control require
intermediate pressure controlled valves having a high degree of
sensitivity and responsiveness with a narrow band of pressures in
order to create the wider pressure "bandwidth" that is needed. In
addition, the ability to accurately generate and transmit the pilot
pressure signal through swivel 238 and into diverter valve 240.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize
that changes may be made in form and detail without departing from
the spirit and scope of the invention.
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